NOTE FOR 2021 READERS: This is the 16th in a series of award-winning open letters to the next century, now just one generation away. Babies born this year in the U.S., and nearly 50 other countries, are expected to live to 2100 and beyond. These letters examine what the world could look like then and how we can make the best scenario happen.
Not the ones in high-rise buildings, although I'm sure plenty more of those exist in your time. Condensed city living makes environmental sense, as do vertical farms; stronger and lighter building materials mean more towers; the international competition for tallest skyscraper is unlikely to end any decade soon.
No, the Elevators I mean are the ones that deserve capitalization: Space Elevators. Were talking super-tall, super-thin tethers that deliver people, satellites and other goods to high Earth orbit in elevator cars the size of trains. If the scientists and engineers who have been theorizing about the Elevator since the 1960s are right, then this is the most ingenious method ever devised for escaping our clingy little gravity well which is responsible for at least 90 percent of the cost of getting to space.
If its as simple as closing the doors and pushing a button that says Zero G, then all your space infrastructure will be delivered on the cheap, without spending a dime on fuel. Theres enough solar energy available, especially at the top of the ride, to power the whole system. Those wild new frontiers weve been talking about (asteroid mining, lunar settlement, cloud cities above Venus, even Mars colonies if you can get around the toxic Martian soil problem) suddenly become way easier to establish.
How long the Elevator ride will take is something you know better than us some say a few days, some say we can get it down to hours. But Im sure youve made plenty of entertainment and intoxication options available in the spacious cars, for when the stunning view gets stale. Besides, slow and steady is more sustainable than a system of chemical bomb-like rockets that spew space junk everywhere. (Looking at you, giant Chinese rocket core that tumbled to Earth as I wrote this letter; Elon Musks SpaceX is no saint when it comes to littering either, shedding its rocket detritus on protected beaches as well as farms.)
The economic argument is as compelling as the environmental one. So SpaceX is proud of reducing the cost of getting stuff to orbit to $6,000 per pound in its rockets, down from $120,000 per pound on the Space Shuttle? Thats cute. Space Elevator scientists say they could get the delivery price down below $100 per pound. Musk says his Starship will end up costing $8 billion to develop and $2 million per ride just for fuel and other operating costs? The Elevator may cost $6 billion or less, and would be relatively low-cost to operate.
Still, half a century after it was first conceptualized, the Elevator dream remains just that a dream. The science is sound, but it also tells us that a tether that tall would carry so much tension that you need to build it out of ultra-strong materials. The steel or aluminum alloys we use to build spaceships wont cut it. We know it has to be some high-tech form of carbon like diamond, but stronger, lighter and more flexible. The current favorite is called single-crystal graphene, but its barely out of the lab.
We could speed up the process if we wanted, of course. NASA could probably build three or four Space Elevators for the $28 billion its spending on returning to the moon. But its hard to summon the will to build something nobody has ever seen. Science-fiction visionaries have done their damnedest to help us imagine it, from our old friend Kim Stanley Robinson to the late, legendary Arthur C. Clarke. Its been 42 years since Clarkes award-winning bestseller The Fountains of Paradise showed a Space Elevator being constructed during you guessed it the 22nd century.
Until this year, I would have said that timeline was too optimistic. But this years news has changed my mind, and now I think theres a strong chance there are multiple elevators in the skies around your planet. Not only are China and Japan making tentative plans for Space Elevator construction, on and off Earth, but a new paper from an engineer at a Canadian university has outlined how we could build a Space Elevator using materials readily available in 2021.
But before we get to that even more impossible-sounding idea, lets stick with the basic science for a moment. If the people of your time are so used to Space Elevators that they seem as dull as the regular variety, its going to be because enough people of our time (your grandparents and great-grandparents) began to truly believe we could build such a thing.
And thats tough, because the idea of a cable going straight up into the heavens does not make intuitive sense. Quite the opposite. To many of us, the Elevator sounds like a beanstalk from a fairy tale, or a Tower of Babel: some kind of vertigo-inducing folly, bound to come tumbling down from the heavens by the end of the story. Weve seen enough monuments to human hubris to suspect that.
But if we think this, its because we forget something else that doesnt make intuitive sense: The Earth is spinning, at the impressive speed of 1,000 miles per hour. This means a tether connected to a space station at the right distance (at least 60,000 miles up), with its center in geostationary orbit that is, traveling above the Equator at 1,000 miles an hour, so the Earth seems to stand still would be as solid as any cable in an elevator shaft.
That explanation still requires math. Heres the analogy that clicked for me when I first wrote about Space Elevators 15 years ago, one that still seems to work for a lot of people new to the concept. Imagine yourself in your yard, spinning around as fast as you can with a tennis ball on the end of a piece of string. Would that string be taut? You betcha so much so that an ant could easily climb from your hand to the ball. Well, the Earth is you, the counterweight space station is the ball, and the Space Elevator is the string. (The only difference is that the Earth never gets tired or dizzy.)
We also have to clear our minds of traditional ideas about how you build something that tall. Russian scientist Konstantin Tsiolkovsky is sometimes credited as coming up with the Space Elevator concept in 1895. But in his highly speculative essays, Tsiolkovsky suggested building from the ground up an orbital tower, basically because hed just seen the Eiffel Tower. That wouldnt work; even with super-strong materials, the base of such a tower would need to be wider than Paris.
It wasnt until 1960 that Soviet engineer Yuri Artsutanov came up with the basics of the idea we know today: You put a satellite in geostationary orbit, with a tether rolled up inside it like a tape measure. Then you extend the tether up into space and down towards the Earths equator at the same time, keeping a perfect balance between the two. Artsutanov had a nice turn of phrase; he called his proposal an Earth-Sputnik-Earth elevator and a heavenly funicular. Unfortunately, his work was published only in Pravda, the Soviet propaganda newspaper, not the big science journals, so the world beyond the Iron Curtain knew nothing about it.
Luckily, U.S. scientists came up with the idea independently anyway. In 1966, four American oceanographers proposed what they called a Sky-Hook that would elongate satellites. (Oceanographers seem to have a curious connection to the history of Space Elevators, which makes sense when you consider they deal with long cables that have to hang under their own weight.) But their proposed tether was too thin, making it an easy target for micro-meteorites. And famed space scientist Jerome Pearson didnt even know about it when he too re-invented the Space Elevator in a 1975 paper.
Pearsons version, at last, lit the blue touchpaper. NASA started paying attention. Arthur C. Clarke, who basically invented the concept of the geostationary communications satellite, got in touch with Pearson and got excited. The Fountains of Paradise was the result; in it, 22nd century engineer Vannevar Morgan battles the naysayers to build an Elevator from fictional hyperfilament, hooking it to the top of a mountain on an equatorial island thats basically meant to be Clarkes home, Sri Lanka. The novel won both the Hugo and Nebula awards, a rarity in science fiction.
For the rest of his life, Clarke only became more excited about the possibility of building an Elevator especially as hyperfilament started to appear for real. Clarkes description sounded a lot like new super-strong carbon-based materials emerging from labs in the 1990s, such as carbon nanotubes. He kept repeating and refining a famous quote that the Elevator would be built about 50 years after everyone stops laughing. In his last interview before he died in 2008, Clarke brought that number down to 10 years.
Honestly, the world should have stopped laughing in 2003. Thats when Bradley Edwards, a NASA-funded physicist who was incensed that the space agency was thinking about Elevator development in terms of centuries, published a seminal book, The Space Elevator. It painstakingly outlined the $6 billion cost, and dropped the mic on just about every potential hazard to the structure. Lightning, wind, hurricanes, space debris, meteorites: None of it was any impediment if you engineered the thing correctly.
(The TL;DR: you taper the tether so its really wide at the top, meaning most debris would leave bullet holes that can be repaired by simple robot crawlers, of the kind we have today; you anchor it to a floating ocean platform so you can move it away from large pieces of space junk, or meteorites we can see coming; since it needs to be on the Equator, you put the platform just off the coast of Ecuador, near the Galapagos, where lightning and hurricanes are historically minimal.)
Edwards is a cheery fellow, and in parts The Space Elevator read like a science fiction novel. In others, it was so stuffed full of equations that it made my head spin. So when I met Edwards at a space conference in 2005, I asked him to boil it down to a single image. What would we see on cable news channels, or the front page of news websites, on the day the Elevator is finally finished? He didnt hesitate. The tether coming down from the sky, he said; a ribbon unspooling steadily towards the floating platform in the Pacific like a stairway from heaven.
The image enchanted me, and I became a Space Elevator true believer for about five minutes. Thats when I ran into Larry Page, the cofounder of Google. The search giant had just gone public, and Page had come to the conference to see if the Elevator was worth investing his newfound billions in. His conclusion? Nah. The physics is fine but Im not sure the chemistry works, Page said. That is, no matter what material you use to construct the tether, no matter how high its melting point or how great its flexibility, the tension involved may be so great that the tether disintegrates at the slightest provocation.
Was Page right? We have no idea; theres no way to run an experiment on the scale required without actually, yknow, building the Elevator itself. And as any engineer will tell you, the only thing we can guarantee is that an obstacle we cant anticipate will appear somewhere down the line. As Clarke writes in The Fountains of Paradise: The Space Elevator was such a leap forward into the unknown that some unpleasant surprises were a virtual certainty.
This is the way Space Elevator news has seemed to go ever since that conference: A brief flurry of excitement followed by a heavy dose of skepticism. Edwards went to work for a number of companies developing superstrong carbon nanotubes; the companies all folded. (To date, no one has produced a carbon nanotube strand longer than 20 inches.) Page didnt invest, but Google X briefly explored a Space Elevator project in 2014, before putting it in deep freeze until the necessary tether materials were ready.
Another NASA scientist, Michael Laine, went into business with Edwards. Then in a twist worthy of a soap opera, he split in search of an earlier IPO and founded LiftPort Group, which demonstrated a robot climber that could travel up to a mile-high tethered balloon. But LiftPort also failed to build a carbon nanotube factory, went bust in the financial crisis of 2008, then reemerged as a Kickstarter in 2012.
We cant build a Space Elevator on Earth today, we just cant, Laine confessed, before pivoting to an unspecified breakthrough that would allow the company to construct an Elevator on the moon by the end of the decade. Indeed, its much easier to build a tether in the low lunar gravity with no atmosphere; in theory, astronauts could return to the moon and build one up there today, no breakthrough required. You could use one of our current crop of widely manufactured superstrong materials, like Kevlar.
Seeking $8,000 to get started, Laine received $100,000 from more than 3,000 backers. But even that wasnt enough to start building the necessary team, he admitted to NJ.com in 2019, and LiftPort fell apart again.
This wasnt the only case of a financial incentive failing to produce results. From 2005 to 2019, the world saw a slew of Space Elevator competitions. Some were funded by NASA, some by the X Prize (the nonprofit that bankrolls contests for major breakthroughs, such as the first private space flight, won by SpaceShipOne in 2004). Some of these prizes were for teams that made their robot climbers go up a tether beyond a certain speed; others were offered for tethers beyond a certain strength (maximum prize offered: $2 million). A few teams won the climber challenges. No team ever won a tether contest.
The embarrassing results of these Space Elevator games was offset by encouraging news from Japan. When Edwards book was published in Japanese, it caused a sensation in the science and engineering communities. In 2012, Obayashi Corporation, one of the countrys largest construction companies, announced its plans to build a Space Elevator by 2050, complete with floating platform. Obayashi vowed that there would be two tethers one up, one down and that the cars would have a capacity of at least 30 astronauts, plus cargo. It put the engineers behind the Tokyo Skytree, the worlds tallest tower, on the project. Doing it by 2050 is quite a lead time, but it does allow the company a realistic three decades to develop tether materials. And at least with Obayashis deep pockets, theres little chance of a LiftPort-style implosion.
Obayashi also had a hand in the STARS-Me project, which sent a tether to space for the first time in 2018. Near the International Space Station, two tiny Cube Satellites strung a tether between them and had a mini-elevator go back and forth. The elevator car is 2.4 inches long; the cable it runs on is 32 feet. Its like testing the concept of trains for the first time by building a model railway in your basement. Nevertheless, there it is, a tiny tether in orbit for the first time, with a second STARS-Me set to launch this year.
At the same time, the chances of seeing a Lunar Elevator in the next decade or so just increased significantly. In April, Chinas space program unveiled plans for a Sky Ladder as part of its next steps towards permanent habitation on the moon. A video released by Chinas Xinhua news agency shows a two-step process, with an Earth-based Elevator lifting an object from the planet and shooting it towards a Moon Elevator, which takes it down to the lunar surface. (China has not specifically announced plans for a Sky Ladder on Earth, but in 2018 a Beijing university boasted that it had carbon nanotubes strong enough to do the job.)
Starting in 2024, NASA plans to ferry astronauts to the moon and back via a bulky Lunar Gateway, a mini-space station derided by critics as an expensive, unnecessary moondoggle. Perhaps if Chinas Sky Ladder turns out to be more effective at delivering payloads to the surface of the moon, a new Space Race will get underway this time, to build a better Elevator.
For Elevator stans, the worlds two largest economies competing to produce a version of their favored space delivery model can only be good news. If China builds a Kevlar-based Elevator on the moon, maybe America will get its act together to build the Earth version first. "Whoever builds the first Elevator will have a virtual monopoly on all future ones: This was something else Brad Edwards told me back in the 2000s. The political and economic structure of the world, he added, could be completely different 50 years from now."
Meanwhile, back on Earth, engineers arent waiting around for these new nanoscale carbon technologies to be ready. Theyre starting to figure out how we can build a kind of Space Elevator with plain old titanium or aluminum by doing something that defuses all the tension from the situation.
Tethers that dont actually connect to the Earth have been hanging around at the edge of Space Elevator theory for some time. The name Skyhook now refers to a tether that just hangs around in the upper atmosphere and rotates faster than the Earth, which means it can grab a spacecraft at the bottom end then launch it into space at the top end like some kind of spinning dog ball launcher. (When it comes to bizarre yet workable space delivery systems, we need as many backyard ball analogies as we can get.)
The idea of a partial Space Elevator a tether that just hangs around motionless in the upper atmosphere has started to attract attention in the past decade. A pair of papers out of McGill University in Canada in 2010 and 2014 suggested that you could build an Elevator out of regular metals that starts 100 miles above the surface of Earth; start any lower than that and the atmosphere gets too dense, too much of a drag on the structure.
Now, 100 miles is a long way up its the edge of Low Earth Orbit, where the sky has already turned black and the stars are out in daytime. But consider that satellites and other spacebound gear are usually trying to get much, much higher. Geosynchronous orbit, where communications satellites live, is up above 22,000 miles. Getting to 100 miles is way easier; you could get there in a spaceplane, like the Shuttle or SpaceShipOne, or in a small rocket launched by balloon. The McGill papers estimate that a partial Elevator could cut the cost of launch missions by about 40 percent compared to regular rockets.
There was one problem with these partial Space Elevator proposals, and thats the Coriolis force. Different parts of the atmosphere move around the Earth at different speeds, so a partial Elevator might be sent spinning in the opposite direction to the planets rotation. (Even on an Earth-connected tether, the Coriolis force could significantly slow Elevator traffic.) Then in March, a York University professor of mechanical engineering named George Zhu (notably, another former oceanographer) published a paper that shows how you could stabilize a partial Elevator. All you need, he says, is to have one car going down at the same time as one goes up.
Its like cable cars moving from a lower spacecraft to an upper spacecraft, Zhu says. They keep going in a loop, they keep it stable. In technical terms, its almost done... Im very confident we will have it by the 22nd century.
Again, this doesnt make intuitive sense. What Zhu is proposing would look something like a giant rubber band, hanging around in the upper atmosphere perpendicular to the Earth. Visualizing it is hard (well, perhaps not if you ingest something psychoactive and stare at the sky for long enough). But if Zhus calculations are right, the rubber band could extend many thousands of miles upwards getting you and your infrastructure into high orbit and beyond for pennies on the dollar.
When I asked Zhu how much this would cost to construct, he did some rough calculations in his head, mostly for the cost of materials like aluminum. I dont know, he said, $100 million? Hes a modest academic type, so I quickly advised him to multiply that by 10 or so if he happens to be in talks with any government agencies. $1 billion for a partial Elevator to Zero-G, reducing space travel costs by 40 percent, is still an incredible deal in any space nerds book. For comparison, the Pentagon's proposed 2022 budget is $715 billion.
Indeed, Zhu believes the major obstacle to building a partial Space Elevator is the increasing quantity of space junk. Which is only going to get worse as Elon Musk and Jeff Bezos launch mega-constellations of satellites, thousands of them, in an effort to bring cheap internet to the world. But unintended consequences abound. Not only are their satellites already making life difficult for astronomers, but scientists agree were at a tipping point for space junk, where the quantity of it will keep increasing even if we stop launching.
Sixty percent of our satellites are dead and falling apart already, and the rest are likely to go out of commission by your century. There are 16,000 pieces of larger debris being tracked so far, plus untold amounts of space dust, all of it traveling at up to 17,500 miles per hour. The more we have of that, the more it threatens all space habitation, not just potential Elevators. Even the most well-designed tapering tether wont hold up to a hailstorm of 21st century junk.
That puts us in mind of the 2021 Netflix movie Space Sweepers, which is set on the cusp of the 22nd century and features a giant orbital structure connected to Earth by multiple Elevators. (Which is exactly what Arthur C. Clarke envisioned as the endgame of all this Elevator building: a vast hoop of habitation around the Earth, like a tire on a wheel.) But its constantly at risk from flying junk, so the working class of the future have to zip around in tiny ships tidying it up.
Zhu is working on a slightly less exciting system, an electrodynamic tether (separate from the Elevator tether) that could attract junk then "de-orbit" it into the atmosphere where it would burn up safely. His team has already launched a test tether in a tiny satellite. With other weird junk-catching tricks such as this alien-like space net already being tested, theSpace Sweepers era is upon us.
Is this our future, then? Until or unless a full-on Earth-tethered Elevator arrives in all its single-crystal graphene glory, we may have to make do with a partial Elevator. Not an express train to space, but a local making a series of stops, from ground to Shuttle to cable car to orbit. All the while the lives of Elevator users are saved by unseen labor, the low-paid clean-up crew, the essential workers who are always there to prop up any major feat of engineering.
That certainly sounds like the less-than-optimal way humanity tends to arrange its affairs. I can just see us filling our journey to the stars with lots of grumbling and shuffling as we shift our luggage from vehicle to vehicle on our way to our weeks in a cut-price inflatable space hotel at the top of the Elevator. Most of us will probably tire of the view before we even deplane, and turn to the entertainment and intoxication options in the lounge.